I don't like JavaScript to much. I have to learn three version of each solution if I want it to work on all the browsers ( Firefox,Safarai,Ie). I find it really frustrating and boring.
Action Script ( Flash ) loads slower but it has the power of being the SAME on all the browsers with flash support.
Action Script works fine as a client side script, in flash. Javascript also runs on the client but it requires 3 rounds of code to do the same thing bugles on all the browsers while the flash AS need only one round :P
Yes, but Java Script is running natively in the browser itself and doesn't need flash player. Also many things in JavaScript can't be done using ActionScript.
So as mira said I consider them different things for different purposes.